The Delaware River.
The Delaware River forms Pennsylvania's eastern border. Across the river are New Jersey and New York
Pennsylvania borders the Delaware River. The river forms part of the boundary between Pennsylvania and New Jersey, but it does not border Ohio. Ohio is located to the west of Pennsylvania and is not directly adjacent to the Delaware River.
The Delaware River forms the boundary between Pennsylvania and New Jersey.
The Delaware River forms the boundary between Pennsylvania and New Jersey.
Lake Eire forms the NW border of Pennsylvania between Ohio and New York State.
New Jersey is located between the Hudson and the Delaware rivers. The Delaware forms the states entire western border and the Hudson is between New Jersey and New York.
The Limpopo forms that border between Zimbabwe and South Africa.
The Colorado River forms the border between Arizona and California
The Limpopo forms that border between Zimbabwe and South Africa.
The border between Mississippi on the west and Arkansas on the east is the Mississippi River. It also forms the border between Arkansas and Tennessee.
The Ohio River forms the southern boundaries of Ohio and Indiana. It begins at the Ohio-Pennsylvania border. It flows southwesterly between Ohio and Kentucky, Indiana and Kentucky, and continues to the Mississippi River.
The Mekong River forms a border between Thailand and Laos.